1. Field of the Invention
The present invention relates to wireless transceivers such as those used in cellular telephones, and in particular, to multiple-band wireless transceivers for use in multiple-band cellular telephones or radio telephones, or mobile stations capable of operation with a cellular network.
2. Description of the Related Art
Demand for multiple-band, e.g. triple-band, wireless transceivers for use in cellular telephones is increasing. Indeed, with multiple cellular telephone network standards in use throughout the world, such a telephone is necessary when travelling from one country to another. In the United States, there is presently at least one system which supports dual band operation, namely the 800 MHz digital TDMA (time division multiple access) and AMPS (advanced mobile phone service) and 1900 MHz digital TDMA, or 800 MHz CDMA (code division multiple access) and AMPS and 1900 MHz CDMA. In Europe, the dual band system supports 900 MHz GSM (global system for mobile wireless service) and 1800 MHz DCS 1800 GSM.
Along with such dual band cellular telephones, there is increasing demand to add a short range radio transceiver capability such as Bluetooth or PAN (personal area network) in the already lightweight pocket cellular telephones now available. This type of short range radio transceiver service is located within the frequency spectrum of 2400-2500 MHz.
Meanwhile, a third generation mobile telecommunications system such as UMTS (universal mobile telecommunications system) is under development. Such systems, it is believed, will also likely require some form of triple-band operation capability, such as, for example, 900 MHz GSM, 1800 MHz DCS1800 and 2.2 GHz UMTS.
The principle challenge of providing multiple-band operation involves the increased costs and form factor requirements of the transceiver architecture needed to support this. For example, conventional approaches to increasing the number of bands of operation involve adding additional RF circuitry in the form of integrated circuits that provide the modulator, demodulator, frequency synthesizing and oscillator functions. In addition to these active components, additional passive components are also needed, such as SAW (surface acoustic wave) filters, resistors, capacitors and inductors, thereby also requiring additional space in the already space-limited handheld devices.
Accordingly, it would be desirable to provide for multiple-band wireless transmitter and receiver operation without significantly impacting the space and size requirements of existing cellular telephone system designs.
A multiple band wireless transceiver with quadrature conversion transmitter and receiver circuits in accordance with the present invention uses a single local oscillator for both transmit and receive operations, thereby providing for time division duplex (TDD) operation. The multiple transmitters share a single modulator while the receivers share a single demodulator. Multiple-band operation is possible while sharing single transmitter and receiver intermediate frequency (IF) filters and one radio frequency (RF) signal source (e.g., voltage controlled oscillator). Any required image rejection or channel selection filters can be fabricated within the same integrated circuit as the remaining transceiver circuitry. As a result, multiple modes of cellular telephone operation can be supported, such as AMPS, D-AMPS (digital AMPS), PCS, GSM, EDGE (enhanced data GSM environment), as well as features compatible with the Bluetooth standard.
A multiple-band wireless transceiver with quadrature conversion transmitter and receiver circuits in accordance with one embodiment of the present invention includes: outgoing data terminals; incoming data terminals; a quadrature signal source; signal generator circuitry; signal conversion circuitry; quadrature modulation circuitry; up conversion circuitry; down conversion circuitry; and quadrature demodulation circuitry. The outgoing data terminals are for conveying baseband outgoing data signals, while the incoming data terminals are for conveying baseband incoming data signals. The quadrature signal source provides first and second pluralities of lower frequency quadrature signals. The signal generator circuitry provides at least one common signal. The signal conversion circuitry, coupled to the signal generator circuitry, receives and converts the common signal to provide first and second pluralities of conversion signals. The quadrature modulation circuitry, coupled to the quadrature signal source and the outgoing data terminals, modulates the first plurality of lower frequency quadrature signals with the baseband outgoing data signals to provide modulated outgoing data signals. The up conversion circuitry, coupled to the signal generator circuitry and the quadrature modulation circuitry, receives and selectively up converts the modulated outgoing data signals with the first plurality of conversion signals to provide higher frequency outgoing data signals. The down conversion circuitry, coupled to the signal generator circuitry, receives and selectively down converts a plurality of higher frequency incoming data signals with the second plurality of conversion signals to provide lower frequency incoming data signals. The quadrature demodulation circuitry, coupled to the down conversion circuitry and the incoming data terminals, receives and demodulates the lower frequency incoming data signals with the second plurality of lower frequency quadrature signals to provide the baseband incoming data signals.
A method for performing multiple-band wireless signal transmission and reception using quadrature signal conversion in accordance with another embodiment of the present invention includes the steps of:
generating first and second pluralities of lower frequency quadrature signals;
generating at least one common signal;
converting the at least one common signal and thereby generating first and second pluralities of conversion signals;
quadrature modulating the first plurality of lower frequency quadrature signals with the plurality of baseband outgoing data signals and thereby generating a plurality of modulated outgoing data signals;
selectively up converting the plurality of modulated outgoing data signals with the first plurality of conversion signals and thereby generating a plurality of higher frequency outgoing data signals;
selectively down converting a plurality of higher frequency incoming data signals with the second plurality of conversion signals and thereby generating a plurality of lower frequency incoming data signals; and
quadrature demodulating the plurality of lower frequency incoming data signals with the second plurality of lower frequency quadrature signals and thereby generating the plurality of baseband incoming data signals.